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-rw-r--r--include/sound/pcm.h3
-rw-r--r--include/uapi/sound/asound.h3
2 files changed, 6 insertions, 0 deletions
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 33451f8ff755..9b187d86e1bd 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -147,6 +147,9 @@ struct snd_pcm_ops {
#define SNDRV_PCM_FMTBIT_S24_BE _SNDRV_PCM_FMTBIT(S24_BE)
#define SNDRV_PCM_FMTBIT_U24_LE _SNDRV_PCM_FMTBIT(U24_LE)
#define SNDRV_PCM_FMTBIT_U24_BE _SNDRV_PCM_FMTBIT(U24_BE)
+// For S32/U32 formats, 'msbits' hardware parameter is often used to deliver information about the
+// available bit count in most significant bit. It's for the case of so-called 'left-justified' or
+// `right-padding` sample which has less width than 32 bit.
#define SNDRV_PCM_FMTBIT_S32_LE _SNDRV_PCM_FMTBIT(S32_LE)
#define SNDRV_PCM_FMTBIT_S32_BE _SNDRV_PCM_FMTBIT(S32_BE)
#define SNDRV_PCM_FMTBIT_U32_LE _SNDRV_PCM_FMTBIT(U32_LE)
diff --git a/include/uapi/sound/asound.h b/include/uapi/sound/asound.h
index 5fbb79e30819..cf1d20e34167 100644
--- a/include/uapi/sound/asound.h
+++ b/include/uapi/sound/asound.h
@@ -202,6 +202,9 @@ typedef int __bitwise snd_pcm_format_t;
#define SNDRV_PCM_FORMAT_S24_BE ((__force snd_pcm_format_t) 7) /* low three bytes */
#define SNDRV_PCM_FORMAT_U24_LE ((__force snd_pcm_format_t) 8) /* low three bytes */
#define SNDRV_PCM_FORMAT_U24_BE ((__force snd_pcm_format_t) 9) /* low three bytes */
+// For S32/U32 formats, 'msbits' hardware parameter is often used to deliver information about the
+// available bit count in most significant bit. It's for the case of so-called 'left-justified' or
+// `right-padding` sample which has less width than 32 bit.
#define SNDRV_PCM_FORMAT_S32_LE ((__force snd_pcm_format_t) 10)
#define SNDRV_PCM_FORMAT_S32_BE ((__force snd_pcm_format_t) 11)
#define SNDRV_PCM_FORMAT_U32_LE ((__force snd_pcm_format_t) 12)